(c) He does not belong to a grade or class of workers of which, immediately before the commencement of stoppage, there were members employed at the premises at which the stoppage occurs, any of whom are participating in or directly interested in the dispute.
If in any case separate branches of work which are commonly conducted as separate businesses in separate premises are conducted in separate departments of the same premises, each such department shall, for the purposes of this subsection, be deemed to be a separate factory, establishment or other premises.